The present invention relates generally to textile yarn winding apparatus and devices and, more particularly, to devices and apparatus by which residual yarn remaining on textile supply bobbins after unwinding may be detected.
In a normal winding operation, yarn supply bobbins are unwound in the winding heads of a bobbin winding machine until completely empty, that is, they leave the winding heads as empty tubes. It can occur, however, that a more or less large winding remnant of residual yarn may remain on a supply bobbin, whose starting end can no longer be supplied inside the winding head to the appropriate yarn guiding members or to a yarn joining device. Empty supply tubes, tubes with a slight residual yarn remnant and tubes with a fairly large, reusable winding of residual yarn ejected from the winding heads are removed jointly onto a common bobbin return path. Since these bobbins must be treated differently, it is necessary to use detectors on the common return path which can recognize and distinguish these different spent bobbins and control their segregation into different transport paths.
The detection and control of segregating spent winding supply bobbins preferably takes place in accordance with the current state of the art mechanically or photooptically. In many instances, however, photooptic sensors are preferred since they are subject to practically no wear, in contrast to mechanical sensors.
German Patent DE-AS 12 78 308 teaches a device in which, initially, bobbins with a fairly large reusable winding remnant and, then subsequently, bobbins with a smaller winding remnant which can no longer be processed are separated from the common return belt, while completely empty tubes are returned directly to the spinning machine. This initial segregation of bobbins with yarn remnants is accomplished at a first branch in the return path via the deflection of a mechanical feeler. A photooptic detector is located further downstream in the return path at a second branch which detector is capable of determining slight remaining yarn remnants. The detector utilizes a radiation source and a photodetector which are selectively arranged in such a manner that the bisecting line between their optical axes coincides with a line which is perpendicular to the surface of the textile bobbin tube and which intersects the vertex of the two optical axes. As a result thereof, the greatest part of the rays impinging upon the surface of the bobbin tube are reflected directly into the receiver lens of the photosensor. In addition, the two optical axes are arranged in a plane which also coincides with the center line of the bobbin tube.
A similar device is known from German Patent DE 40 08 795 A1, which exhibits the same features but in which relative motion between the detector and the bobbin required for detecting the yarn remnant is generated by the movement of the detector along the bobbin.
Disadvantageously, the known devices above-described do not always function with the desired reliability.